A PC, in which a first casing with a keyboard portion and a second casing with a display portion having touch operation function using hand can open and close 360 degrees relative to each other, due to its function using a biaxial hinge, is called tablet notebook PC in general. The tablet notebook PC of this type, in which a first casing and a second casing as described above can open and close 360 degrees relative to each other, is made known by JP Laid-Open Patent Application No. 2009-063039. However, in such tablet notebook PC, a user may either use it as an ordinary notebook PC by inputting using a keyboard portion provided on the first casing, when the second casing is opened relative to the first casing, or as a tablet PC, by putting it on a table such as desk, the first casing and the second casing having rotated 360 degrees relative to each other to a folded state, and by inputting on a display portion by means of touching operation using his hand. In this case, when a terminal device is used in a folded state and a keyboard portion provided on a first casing still remains protruding from the upper surface of the first casing, a contact of the keyboard portion with a surface of the table results in erroneous operations, which is problematic. Or otherwise, when rubber feet are provided on the lower surface of the first casing, these rubber feet touch the backside of the second casing, so that the two casings cannot be folded to a horizontal position, which is again problematic. However, conventional biaxial hinges cannot solve the above-mentioned problems.